For the purpose of understanding the invention it is useful to have a basic understanding of Mobile IP. Mobile IP (v4/v6), also indicated as MIPv4 [MIPv4] and MIPv6 [MIPv6], enables a mobile node (MN) to register its temporary location indicated by a care-of-address (CoA) to its Home Agent (HA). The HA then keeps a mapping (also called a binding) between the MN's permanent address, otherwise called Home Address (HoA), and the registered CoA so that packets for that MN can be redirected to its current location using IP encapsulation techniques (tunneling).
The CoA used by a MN can be an address that belongs to a Foreign Agent (FA) when MIPv4 is used or, in MIPv4 and MIPv6, it can be a temporarily allocated address to the MN itself in which case is called a collocated care-of-address (CCoA).
The concepts and solutions described here are applicable to both MIPv4 and MIP unless otherwise mentioned.
Regional tunneling (REGTUN) is one technique sometimes used in conjunction with Mobile IP. This approach uses a Gateway Foreign Agent (GFA) between the FA and the HA to improve MIP signaling. Specifically, the MN can register the local GFA CoA into the HA using an MIP registration with the HA that is routed via the GFA. Then each binding update under the same GFA goes just to the GFA instead of the HA, and changes the FA CoA for the GFA. The GFA switches the GFA CoA traffic for the specific HoA into the FA CoA matching that HoA and GFA CoA. The GFA update is a regional registration and it avoids having to refresh the HA on each hand-off which is a bandwidth and latency gain because the HA could be a very distant node from the FA/GFA.
The problem with this draft (http://www.ietf.org/proceedings/01dec/I-D/draft-ietf-mobileip-reg-tunnel-05.txt) is that the signaling scheme assumes that the two addressing schemes are the same either side of the GFA, and no support is enabled for dynamic HA allocation, both of which are common requirements in MIP. Therefore, a need exists for apparatus and methods that will support disparate addressing plans and dynamic HA address allocation in MIP signaling.